This invention concerns a desulfurizing agent suitable for removing SO.sub.2 and /or H.sub.2 S in a fluidized bed type heating furnace.
A fluidized bed heating furnace has various merits in that it can use low calory fuels or bulky fuels, operate at low NO.sub.x value and facilitate desulfurization of exhaust gases, as well as requiring less installation cost. In view of such merits, the fluidized bed heating furnace is now being utilized more and more in various types of combustion furnaces, incinerators for city dust and sludge for gasifying furnaces for solid fuels, etc.
Since it is now necessary to use fuels of high sulfur content or to gasify solid fuels of high sulfur content or to gasify solid fuels of high sulfur content because of the recent increases in energy cost, the sulfur concentration in exhaust gases or product gases from the fluidized bed heating furnace is inevitably increased. In addition, since city dust or sludge is mainly composed of waste matter such as garbage and sewage and contains sulfur at high concentration, exhaust gases, which are the result of burning such waste matter, also contain a high level of sulfur, which leads to undesired atmospheric pollution.
In view of such increasing environmental contamination, and in order to balance the conflict between the pollution caused by industrial waste and the clean atmosphere desired by human beings, there is a strong demand for a desulfurizing agent of high performance at a low cost and easy to handle. However, the desulfurizing agents available at present are not always satisfactory from the foregoing viewpoints.
Those desulfurizing agents employed so far in the fluidized bed heating furnance as a heat medium and desulfurizer include natural carbonate ores such as limestone or dolomite which are mainly composed of CaO or MgO, as well as industrial products such as portland cement clinker or a hardened hydration product of portland cement mainly composed of CaO, but these products have inherent merits and demerits. Namely, limestone and dolomite are available at low cost. However, since they are sedimentary ores having water content and great density, they tend to collapse and to issue a large volume of scattered dust when used as a heating medium and do not attain a sufficient desulfurizing effect unless they are used in great amounts. Furthermore, although the cement clinker or the hardened product of cement can be used stably as the heat medium, they fail to provide a sufficient desulfurizing effect.